Three years ago ACIAR commissioned reviews of the impact assessment studies. These summarised the overall return of ACIAR’s research and development (R&D) investments and also assessed the consistency of the studies. A range of independent consultants are commissioned to undertake these assessments so it was not surprising that the reviewers found that there was variability in the detail, rigour and presentation of the results. Therefore we decided to develop a set of guidelines for all independent consultants to use as a basis for future assessments. The aim of the guidelines is to ensure consistency in the methodological approaches used, the treatment of information collected and presentation of the results.